This seems like a simple query to me. Correct me if I am wrong but as
I understand it you want to get a list of SwReleases that a user has
access to. Would something like this not work
SELECT s.ID, s.Name
FROM SwRelease as s
WHERE s.ID IN (
SELECT SwID
FROM GroupSwRel -- this table is the group to SwRelease relation ship
WHERE GroupID IN (
SELECT GroupID
FROM UserGroupRel -- this table is the user to group relationship.
WHERE UserID = 'someuserid'))
I've never done a query with a sub query in a sub query but it seems
like it should work to me. In fact, if I'm not mistaken you may be able
to rewrite this just using joins.
Chris W
David T. Ashley wrote:
Hi,
I'm implementing a software release database. Users may aribtrarily be
members of groups (a many-to-many mapping), and each software release may
contain multiple files.
I'd like to allow users the maximum flexibility in deciding who may view
what software releases. The most obvious approach is to allow
specification
in the form of "Release X may be viewed by Users in Group Y or Group
Z", per
release.
In this case, the database design would be something like:
[Users] (many:many) [Groups] (many:many) [SwReleases] (1:many) [Files]
The many:many relationship between groups and software releases
specifies a
Boolean function, of the form "is in Group X or is in Group Y or ...".
Since one knows the user who is logged in (for a web database), one
can do
an outer join and quickly find all the software releases that the user
may
view. I believe one can do it in O(log N) time.
However, the Boolean function is of a fairly special form ("is in
Group X or
is in Group Y ..."). This is the only form where it seems to
translate to
an SQL query naturally.
Here is my question:
Is there any interesting way to structure a database so that other
forms of
permissions can be specified and translate directly into SQL queries?
For example, what if, for a software release, one says, "to view this
software release, a user must be in Group X or Group Y, but not in
Group Z
and not user Q"? Is there a database structure and a corresponding
O(log N)
query that will quickly find for a given user what software releases
may be
viewed?
Thanks.
--
Chris W
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